There are many circuits, particularly voltage level detector circuits which must discriminate between two voltage levels. A common element of these circuits is that a reference voltage level must be established around which the level detection is founded.
Problems exist, however, when it is understood that the voltage level must be stabilized for temperature changes. Many standard circuits are now available which provide for very stable voltages over wide temperature swings. The problem is that some detector circuits themselves change their internal parameters dependant upon temperature. Thus, in these situations, the reference voltage must also change with respect to temperature to compensate.
A further problem exists in that in some situations, such as a ECL to CMOS logic level conversion circuit, there are different standards to which the reference voltage must be keyed. One of these standards requires the reference voltage to change with temperature while the other standard requires a reference voltage which is constant with respect to temperature changes. It is important to have a reference voltage which is easily converted from one standard to the other with a minimum of difficulty.
This problem is compounded in that, as discussed above, a constant reference voltage can not be used in any event due to changes in the converter circuit.
Thus, a need exists in the art for a voltage reference circuit which changes reference levels based upon temperature gradients with the rate of change very precisely controlled and matched to a given set of circuit components.
A further need exists in the art for such a circuit which can easily be adjusted to have different temperature coefficients to meet different standards.